1. Field of the Invention
This invention relates generally to semiconductor integrated circuit devices and more particularly, to transformers manufactured on semiconductor integrated circuit chips and even more particularly, to transformers manufactured on semiconductor integrated circuit chips that can be used at video and radio frequencies as well as other applications.
2. Discussion of the Related Art
There have been various attempts shown in the prior art to construct workable chip type transformers. One such attempt is shown in U.S. Pat. No. 5,497,137 entitled "Chip type transformer" issued to Yasuhiro Fjuiki of Nagaokakyo, Japan in which a balun type transformer is constructed as a chip type transformer in which there is a laminate having five dielectric substrates superimposed on one another. A ground connection is formed on one main surface of the first dielectric substrate and a ground connection is formed on the main surface of the fifth dielectric substrate. A connecting electrode is formed on one main surface of the second dielectric substrate and a first strip line is formed on one main surface of the third dielectric substrate. The first strip line consists of a first spiral portion and a second spiral portion. A second spiral strip line and a third spiral strip line are formed on one main surface of the fourth dielectric substrate and the second strip line and the third strip line are electromagnetically connected with the first portion of the first strip line and the second portion respectively.
Another such attempt is disclosed in U.S. Pat. No. 4,547,961 entitled "Method of manufacture of miniaturized transformer" and invented by Bokil and Morong and discloses a miniaturized thick-film isolation transformer comprising two rectangular substrates each carrying successive screen-printed thick-film layers of dielectric with spiral planar windings embedded therein. The spiral windings comprise conductors formed of fused conductive particles embedded within a layer of dielectric insulating means solidified by firing at high temperature to form a rigid structure with the windings hermetically sealed within the dielectric and conductively isolated from each other within the transformer. The substrates are formed at opposite ends thereof with closely adjacent connection pads all located at a single level to accommodate automated connection making and connections between the pads and the windings are effected by conductors formed of fused conductive particles. The substrates and the dielectric layers are formed with a central opening in which is position the central leg of a three-legged solid magnetic core. The remaining portions of the core surround the two substrates to form a compact rugged construction especially suitable for assembly with hybrid integrated circuit components.
U.S. Pat. No. 4,785,345, entitled "Integrated transformer structure with primary winding in substrate" and invented by Rawls and Turgeon, and discloses an integrated transformer structure. In one embodiment, the primary transformer winding is formed using dielectrically isolated technology to isolate high voltages applied to the transformer from other components in the substrate. Alternatively, conventional junction isolated technology may be used, where physical separation between the integrated transformer and other components may be provided. The primary winding comprises a planar spiral formed with a low-resistivity material and incorporated with the substrate and an insulating layer formed over the primary winding. A planar spiral configuration is also used to form the secondary winding and is formed on top of the insulating layer directly above the primary winding.
U.S. Pat. No. 4,717,901 entitled "Electronic component, especially for a chip inductance" and invented by Autenrieth, Marth, and Schindler, discloses an electronic component which includes a solid core part having a perpendicular prismatic spatial shape and lateral surfaces, the core part having a recess in the form of a blind hole formed therein defining a winding space, and electrical contact layers disposed on at least some of the lateral surfaces of the core part.
U.S. Pat. No. 5,477,204 entitled "Radio frequency transformer" and invented by Li, discloses a transformer having a substrate on which two substantially adjacent runners are disposed. The two runners have substantially the same width and the same length and run from one segment of the substrate to another forming two spirals which run in opposite directions.
U.S. Pat. No. 5,414,402 entitled "Multi-layer substrate" and invented by Mandai, Kato, and Tojyo, discloses a multi-layer substrate which should be used with an inductor. The multi-layer substrate has an internal coil which is connected with the inductor electrically and the internal coil has such an inductance value that the total inductance of the inductor and the internal coil is a specified value.
None of the prior art shows a simple construction of a transformer that can be constructed easily and simply on a semiconductor integrated circuit chip. What is needed is transformer layout that can be adapted for use in different and diverse applications including IF, RF, and Video frequencies in which the magnetic coupling between the primary and secondary can be designed and obtained during manufacture.